Electric furnace.



J.-L. DIXON.

ELECTRIC FURNACE.

APPLICATION FILED APR. 10, 1916.

Patented Sept. 5, 1916.

2 SHEETS-SHEET 1.

' JOSEPH LAWTON Dixon, or DETROIT, MICHIGAN.

ELECTRIC FURNACE.

Specification 01 Letters Patent.

Patented Sept. 5, 1916.

' Original application filed February 23, 1915, Serial No. 9,782. Divided and this application filed April 10,

1916. Serial No. 90,083.

and use the same.

My present invention relates to that class of electric smelting furnaces wherein the current may be made to pass either from one electrode to another over the bath or from one or more of these either wholly or in part through the bath and furnace lining.

The object of my invention is to supply an improved construction for electric smelting furnaces of this description whereby currents fed from specially arranged transformers are made controllable as to their phase relations by suitable switches, so as to cause different proportions of thetotal current to flow through the bath and lining.

it is a further object of the invention to accomplish this with either three-phase or two phase systems, and without unbalancing the load on the main leads.

Certain preferred embodiments of my invention are illustrated in the accompanying drawings, wherein Figure 1 is a diagrammatic illustration of one form of the invention delivering two phase currents in the furnace, Figs. 2 and 3 are vector diagrams showing the different phase relations producible by use of the switches shown in Fig. 1, Fig. 4 is a. diagrammatic illustration of the invention as modified for use of six upper electrodes supplied with three-phase currents and Fig. 5

and 6 are vector diagrams showing the different phase relations producible by use of the switches shown in Fig. 4. i

in Fig. 1, the usual hearth, crucible or container is shown-at 10, the molten bath within it is shown at 11, while the four upper electrodes 12, 13, 14 and 15 project downward toward the bath through the insulating cover 16. The current which passes downward through the bath when so desired, returns through the lower electrode 17 The working currentis derived from the three-phase alternating current mains, 18,-

1t) and 20, through three transformers, 21, 22 and 23.

The secondary terminals of the transformer 21 are connected respectively to the upper electrodes 12 and 13. The outerterminals of transformers 22 and 23 are connected respectively to the upper electrodes 14 and 15 and their inner or intermediate terminals are connected in common to'the lower electrode. I may also connect the middle point of the transformer secondary 21 with the lower electrode, as shown. As shown the primaries of these transformers are connected to the three-phase main leads so that the secondaries shall yield two phase currents, and the primary currents are controlled by the two multiple switches 24 and 25. By means of these switches one of the pair of transformers 22, 23 can be used either so that its secondary current is coin- 7 cident with or exactly opposed to that of the other of the pair. Thus, with the switches 24 closed and the switches 25 open, the currents in the upper electrodes will have their phases in accordance with the diagram in Fig. 2. Here, if the current is unity in all the upper electrodes, no current will pass through the bath to the lower electrode. If, on the contrary, switch 25 be closed and switch 24 be open, the phase relations in the upper electrodes will be as shown in Fig. 3; and then, if the current be unity in all of these upper electrodes, the current passing through the bath will be equal to the entire current supplied by the two transformers 22 and 23. In either of these cases there will be no unequal loading of the mains, provided the transformer 21 supplies power equal to that supplied by the other two transformers.

WVhere larger furnaces are used, employing say six upper electrodes, the arrangement may be modified as in Fig. 4. Here four transformers 26,- 27, 28 and 29 have their respective primary terminals connected to the mains 18, 19 and 20. The connections may be permanent, as shown, for three of these, while theconnections of the fourth are controlled by the multiple switches 30 and 31.

The terminals of the secondaries of the transformers 26 and 27 are connected respectively to the four upper' electrodes 32, 33, 34 and 35. The other terminals of the secondaries of transformers 28 and 29 are coi iected respectively to the upper electrodes 36 and 37, while their intermediate terminals are connected to the lower electrode 17.

The transformers 28 and 29 form a pair whose primaries can be mutually reversed by appropriate use of the switches 30 and 31.

When the switches 30 are closed and switches 31 open the phase relations in the upper electrode are as shown in Fig. 5; in which case, assuming a current equal to unity in each upper electrode, no current will pass through the lower electrode. If switches 31 are closed and switches 30 open, the phase relations in the upper-electrodes are as in Fig. 6. In this case, the entire current supplied by transformers 28 and 29 will pass through the bath to the lower electrode. In each of the forms shown therefore, there is a pair of transformers so arranged as to be capable of either supplying their joint power for action through the bath, or, on the other hand, if desired, to neutralize each other, so far as action through the bath is concerned so as to reduce the current in the lower electrode to zero. At the same time there will be no unequal loading of the main leads, provided, in the form shown in Fig. 1, the transformer 21 supplies power equal to the total supplied by transformers 22 and 23; and, in the form shown in Fig. 4, each transformer 26 and 27 supplies power equal to the power supplied by transformers 28 and 29 united.

This application is a division of my earlier application for improvement in electric fprnaces, filed February 23, 1915, Serial N o. 9 82. Y

' What I claim is.:

1. An electric furnace having upper elec trodes in pairs and a lower electrode, main leads for supplying alternating current, one or more transformers whose secondaries are connected to all but one pair of said upper electrodes, a pair of additional transformers whose secondaries are connected to the remaining pair of upper electrodes and to the lower electrode, conductors connecting the primaries of said transformers to said main leads and means for altering the connections of the primaries of said additional pair of transformers so as to make their secondaries either oppose or aid each other.

- 2. An electric furnace having upper electrodes in pairs and a lower electrode, main leads for supplying three phase alternating currents, one or more transformers whose secondaries are connected so as to deliver two-phase current to all but one pair of said upper electrodes, a pair of additional transformers whose secondaries are connected to the remaining pair of upper electrodes and to the lower electrode, so as to deliver twophase current thereto, conductors connecting the primaries of said transformers to said main leads and multiple switches in the conductors leading to said additional pair of transformers adapted to reverse the action of one of the members of said pair with relation to the other member.

3. An electric furnace having upper electrodes in pairs and a lower electrode, main leads for supplying three-phase alternating currents, one or more transformers whose secondaries are connected so as to deliver two-phase currents to all but one pair of said upper electrodes, a pair of additional transformers whose secondaries are connected to the remaining pair of upper electrodes and to the lower electrode, so as to deliver twophase current thereto, a connection between one main lead and the outer primary terminal of the first named transformer group,

a connection between the opposite primary terminal of the first named group and the middle points of the remaining two primaries, and switches adapted to reverse the effect of one of the primaries of the additional transformers with respect to the other.

In testimony whereof, I have afiixed my signature.

JOSEPH LAWTON DIXON. 

